Hello! Thanks for taking the time to visit the project! 

This post will explain all costs associated with assembling a PR-Holonet unit, activating it, and operating it. In the ballpark of things, the cost of building a PR-Holonet system as presented in this post will vary from $420 to $600 depending on your final configuration. The differences only affect the capacity of the system to operate in the absence of enough sunlight; as well as the capacity to power/recharge other equipment or the ability to recharge and keep the system operational at the same time. It does not affect the core functionality of sending and receiving messages. It also bears mentioning that I will not be covering shipping costs or taxes. The system has been designed to minimize the difficulty of sourcing the components needed as well as to be used pretty much anywhere; but that also means that I can't, in good faith, give good numbers on shipping costs or taxes to cover all scenarios for anyone to build it.

All cost estimates provided in this post will be in US dollars. Please convert as necessary if you are living in another country. 

This log is long, and it contains a lot of information. I may break it up later in the future. For now, grab a snack, turn some music on, and enjoy.

Thank you!

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Assembly Costs

The two key components of this system, the Raspberry Pi 3 B and the Rockblock MK II, should be available at fixed pricing.

The rest of the costs may vary depending on sourcing or capacity. The list of items is as follows:

• A portable cellphone battery charger
• A foldable solar cell charger
• A non-metallic project box (ideally water-proof)
• A microSD memory card
• Female to female jumper cables
• Spare micro USB cables

PR-Holonet is meant to be used in emergency and technology-austere environments. For this reason, the actual list of parts has been put together to enable a system that can:

• Work on its own
• Power, enable, or leverage other tech equipment that can be of use to help relief efforts

Following is a list of the actual parts and costs being used to build the system. For a budget version of the system, see the end of the post.

Total Kit Cost: $600

System Core

The core is made up of the Pi, Rockblock, female to female jumper wires, microUSB cables, and microSD card.

Part Name	Description	Cost ($)	Source
Raspberry Pi 3 B	The brains of the operation	$35.00	Adafruit
RockBlock MK II	Iridium Short Burst Data transceiver	$249.50	Sparkfun
Samsung EVO microSD card	Capacity - 64GB Class 10 UHS 3 Speed - Write: 60Mbps - Read: 90Mbps	$19.99	Amazon
Female to Female Jumper Wires	- 20-pack tape - 6 inches each - .1" pitch	$1.95	Sparkfun
Anker Micro USB Cables	Two microUSB cables that can be used to power the Pi or charge the battery	$9.99	Amazon

Project Case

To allow the project to be weather resistant, I've selected a dust-proof, water resistant project box. Down the road I'd like to really test out how hot the system gets and actually test its water-proof worthiness, for now the current case gets the job done.

Part Name	Description	Cost ($)	Source
Uxcell Junction Box DIY Case Enclosure Gray	Dimensions - 250mm x 150mm x 100mm Dustproof IP65	$21.99	Amazon

Power System

The battery and solar charger components are the systems that will vary in cost the most. They are also the components that will dictate whether PR-Holonet can be used to increase the number availability of USB powered tech for relief efforts. The main trade-off in choice selection will boil down to: 

• Ability to charge the battery and power PR-Holonet simultaneously
• Ability to use the battery to operate PR-Holonet without interruptions and charge a phone or other USB device 
• Ability for the solar charger to charge the system battery and another USB device simultaneously
• The time it will take the solar charger to fully charge the system battery under ideal sun conditions

The list of components that will provide the best capability under the current design is: 

Part Name	Description	Cost ($)	Source
BatPower PROE 2 ES10 40000mAh Battery	Dimensions - 7.2 x 3.2 x 0.7 inches Capacity - 40000 mAh Useful Features - Can be charged by microUSB cable or 18V barrel charger - Integrated LED "Flashlight" - Can charge itself and power/recharge systems simultaneously - Can be used to power a laptop - Can output up to 90W of power	$169.99	Amazon
ALLPOWERS 36W Foldable Solar Charger	Dimensions - 12.8 x 7.7 x 3.1 inches Weight - 3.02 pounds Useful Features - Higher number of PV cells than ~20W systems means more comparative power for the same amount of sun - Two 5V/2.4A ports ( up to 12W output per port) - One 18V/1.5A port ( up to 27W ) - If your battery supports 18V power input, then it can charge faster than using regular USB 2.0 to charge it - Water-resistant (according to marketing material)	$89.99	Amazon

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Activation Costs

Activation costs are comprised of 3 parts:

• The satellite gateway communications service (Rock7 CORE)
• The cloud data processing service (Amazon AWS: Lambda, S3)
• The cellular number and message routing service (Twilio)

None of these services require a contract, so the system can be used for the time needed and then deactivated. 

Rock7 Core 

To use the Rockblock MK II, a monthly activation fee of an estimated $14 is required. There is no minimum yearly commitment required. Use as needed.

Amazon AWS (Lambda Services) 

Amazon's pricing model is based on resource consumption. PR-Holonet easily falls in their free of cost range. However, you will need to create an account and enter your credit card information. No contract required. 

Twilio

Twilio charges a monthly fee for providing phone numbers. The fee can vary, in my case it is $3 per month for 1 number. Data is billed per message. No contract is required.

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Operating Costs

Operational costs, for the effect of this post, will refer to any costs other than monthly activation fees. For PR-Holonet, this is encompassed by the data transmission and handling costs. PR-Holonet is a low-bandwidth communications system; the data transmission costs are due in its majority to the satellite gateway services. 

The operational costs are also encompassed by the same three services mentioned in the previous section: 

• The satellite gateway communications service (Rock7 CORE)
• The cloud data processing service (Amazon AWS: Lambda, S3)
• The cellular number and message routing service (Twilio)

Rock7 Core

Rock7 charges for every message sent and received over its satcom gateway. Some RockBlock actions, such as pinging the servers for pending messages, may incur in costs. All costs are based on a unit of cost called a "credit". A credit is any burst of data sent or received from a RockBlock MK II that is 50 bytes or less. All transmitted and received data is charged based on the "credit" scheme. 

The cost of each credit is based on the total amount of credits acquired at the time of purchase. Credits do not expire and can be used so long as there is an active account and Iridium transceiver available. Credits are also shared among all Iridium devices registered to it. 

At present the prices for credits are (amount of dollars subject to change based on currency exchange values): 

Number of Credits	Cost per Credit British Pounds (£) / US Dollars	Bundle Price British Pounds / US Dollars ($)
100 Credits	£0.11 / $0.15	£11.00 / $15.16
200 Credits	£0.10 / $0.14	£20.00 / $27.56
500 Credits	£0.09 / $0.12	£45.00 / $62.01
1000 Credits	£0.08 / $0.11	£80.00 / $110.24
2000 Credits	£0.07 / $0.10	£140.00 / $192.92
5000 Credits	£0.06 / $0.15	£300.00 / $413.40
10000 Credits	£0.05 / $0.08	£500.00 / $689.00
20000 Credits	£0.04 / $0.06	£800.00 / $1102.40

Amazon AWS (Lambda Services)

Amazon AWS is NOT FREE. However, due to the low use of computational resources required by PR-Holonet it falls within the no-charge tier for Lambda services. Thus, there is no additional impact to operating costs because of cloud processing. 

Twilio

Twilio charges $0.0075 per message for the first 5 million messages routed through their services in the US.

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An alternative, budget version of PR-Holonet

If cost is a priority, here is a version of PR-Holonet that will get you a working system for close to $200 less in parts. Be mindful that you compromise:

• Ability to charge the battery and power PR-Holonet simultaneously
• Ability to use the battery to operate PR-Holonet without interruptions and charge a phone or other USB device 
• Ability for the solar charger to charge the system battery and another USB device simultaneously
• The time it will take the solar charger to fully charge the system battery under ideal sun conditions

Total Kit Cost: $418.85

System Core

Part Name	Description	Cost ($)	Source
Raspberry Pi 3 B	The brains of the operation	$35.99	Adafruit
RockBlock MK II	Iridium Short Burst Data  transceiver	$249.50	Sparkfun
Samsung EVO microSD card	Capacity - 32GB Class 10 UHS 3 Speed - Write: 60Mbps - Read: 90Mbps	$12.99	Amazon
Female to Female Jumper Wires	- 20-pack tape - 6 inches each - .1" pitch	$1.95	Sparkfun
Anker Micro USB Cables	2  microUSB cables that can be used to power the Pi or  charge the battery	$9.99	Amazon

Project Case

Part Name	Description	Cost ($)	Source
Uxcell Junction Box DIY Case Enclosure Gray	Dimensions - 250mm x 150mm x 100mm Dustproof IP65	$21.99	Amazon

Power System

Part Name	Description	Cost ($)	Source
Anker 13mAh Battery	Dimensions - 7.2 x 3.2 x 0.7 inches Capacity - 13000 mAh	$31.99	Amazon
Allpowers 21 W Foldable Solar Charger	Dimensions - 12.8 x 7.7 x 3.1 inches Weight - 3.02 pounds Useful Features - Integrated 6000mAh battery	$54.99	Amazon

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References, Links, and Resources

1. Amazon.com [ https://www.amazon.com/ ]
2. Sparkfun.com [ https://www.sparkfun.com/ ]
3. Adafruit.com [ https://www.adafruit.com/ ]
4. Amazon Lambda Pricing [ https://aws.amazon.com/lambda/pricing/ ]
5. Amazon S3 Pricing [ https://aws.amazon.com/s3/pricing/ ]
6. Rock7 Core Pricing [http://www.rock7mobile.com/products-rockblock ]
7. Twilio Pricing [ https://www.twilio.com/sms/pricing/us ]

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You Made It!!

That is the end for this log. I hope it has provided a clear understanding of the costs associated with building and operating PR-Holonet. If you have questions, send them my way!